Systematic assessment of dredged sludge dewaterability improvement with different organic polymers based on analytic hierarchy process.

Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch (CS) and poly-dimethyl diallyl ammonium chloride (PDDA) on dredged sludge dewatering efficiency and residual water quality of Baiyangdian lake were comprehensively investigated and evaluated by analytic hierarchy process (AHP). The results indicated that PDDA had stronger electrical effect and flocculation performance compared with CS, resulting in more efficient dewatering performance. PDDA can reduce the pollutants of discharged residual water, while CS significantly promoted the increase of NH4+-N and NO3--N in the residual water. The increase of NH4+-N in the residual water of CS was due to the release of dredged sludge, while the increase of NO3--N was introduced by CS leaching. AHP showed that PDDA performed better in flocculation treatment of dredged sludge than other organic polymers. This work provides a method for optimization of flocculation treatment for dredged sludge dewaterability.